The invention relates to an apparatus for producing a three-dimensional part, particularly a laser sintering machine and, more particularly, a synthetic material laser sintering machine.
Known laser sintering machines comprise a machine housing in which a sinter building space or process space is arranged. In the upper region of this building space, the exit optics of a sintering laser in the form of a scanner are located. The scanner constitutes the optical system for deflecting the laser beam providing the energy required for sintering the sinter material (thermoplast powder). Below the optical system, there is a work piece platform being height adjustable and above which material feeding means including a coating device are provided, designed for feeding powdery sinter material from a reservoir in the process area of the work piece platform.
Laser sintering machines in the prior art, the part is built in a layer-by-layer fashion in the inner region of the height-adjustable work piece platform. However, in order to prevent the thermoplast powder, which is not illuminated and thus not sintered, from falling off the work piece platform, a rim serving as a delimitation of the work piece platform is formed, i.e. sintered, substantially simultaneously at the periphery of the platform.
This approach has drawbacks in several respects.
Building the rim on the work piece platform requires additional exposure time and also, additional thermoplast powder is needed which can no longer be used.
In addition, as a particular drawback, in the case of a building error, a sufficiently strong box-like delimiting structure is not formed and may lead to deformations and thus to rejects even before or, at the latest, while withdrawing the part from the height-adjustable platform.
Furthermore, when withdrawing the work piece platform from the laser sintering machine, rim fractures or rim damages cause some powder to drop into the lower region of the laser sintering machine, soiling this portion and thus causing additional servicing and down-time of the laser sintering machine.
As a further serious drawback to all the above, the sintered part as well as the delimitation have to remain in the laser sintering machine for a certain period after the actual production process, in order to obtain a degree of curing and cooling such that deformations of the edge and of the part will no longer occur during withdrawal. As a rule of thumb associated herewith, a building time of 20 hours would also require a cooling time of roughly 20 hours for the built rim and the part, such that prior art laser sintering machines have relatively long down-times.
It is an object of the invention to from an apparatus for producing a three-dimensional part and particularly a laser sintering machine such that the amount of energy and material needed can be lowered and the down-time between two building processes can be significantly shortened.
The invention provides an apparatus for producing a three-dimensional part by successive layer-by-layer solidification of a solidifiable material at locations corresponding to the cross section of the part, and having a building space (3) provided in a machine housing, characterized in that an interchangeable container (12; 112) forming a delimiting frame for the material (9) can be inserted within said building space (3), in which a work piece platform (8; 108) is integrated and a supporting device is arranged, on which the work piece platform (8; 108) is supported and/or mounted during operation of the apparatus.
Preferred embodiments of the invention additionally include one or more of the following features:
(1) the work piece platform is adjustable in height within said delimiting frame and integrated in the interchangeable container as a container bottom; building space (3) is located in a machine housing and wherein exit optics (5) of a sintering laser are arranged in said building space (3) and said work piece platform (8) is arranged below said building space, and that material feeding means with a coating device (10) for feeding powdery sinter material (9) from a reservoir in the process area of said work piece platform (8) are provided;
(2) the work piece platform (8) can be latched to the side walls (14) of said interchangeable container (12); in a lower withdrawing position and the interchangeable container (12) can be withdrawn in the latched state from said building space (3) together with said work piece platform (8) forming its container bottom;
(3) the latching between the side walls (14) of said interchangeable container (12) and the work piece platform (8) is carried out by sliding plugs (25) insertable into bores aligned with respect to each other;
(4) the interchangeable container (12) in plan view has a substantially square or rectangular cross section and comprises four side walls (14) substantially perpendicular to each other, in which said work piece platform (8) is guided in a height-adjustable manner;
(5) the supporting device (20) for said work piece platform (8) is engaged through engagement recesses (33) in the rear side wall (14xe2x80x2) and extending in the direction of displacement;
(6) the supporting device (20) for said work piece platform (8) is engaged through engagement recesses (33) in the rear side wall (14xe2x80x2) and extending in the direction of displacement:
(7) the supporting device (20) is guided in the area of the machine rear wall;
(8) the supporting device (40) is incorporated in the lower portion of said interchangeable container (12) and is therefore a fixed component of said interchangeable container (12);
(9) the interchangeable container (12) can be inserted into guides (70) in the portion of the side walls (14) of said building space (3);
(10) the interchangeable container (12) is provided at its upper end with supporting angles (71) laterally extending away and resting on the guides (70) of said machine housing (2);
(11) the engagement recesses (33) are covered in a powder proof manner in the portion above said work piece platform (8);
(12) the sealing of said engagement recesses (33) is carried out by a roller shutter (34);
(13) the upper end (35) of said roller shutter (34) is mounted to the upper edge (36) of the rear side wall (14xe2x80x2);
(14) the roller shutter (34) is a steel roller shutter;
(15) the work piece platform (8) is formed by two spaced bottoms arranged in parallel to each other, the upper bottom forming the work piece holder and the lower bottom resting on said supporting device (20);
(16) magnet elements (4) cooperating with said roller shutter (34) are arranged adjacent to said engagement recesses (33);
(17) the roller shutter (34) is guided by a deflection pulley (60) the rear edge of which is aligned with the inner surface of the rear side wall (14xe2x80x2);
(18) a powder compression element is active between the inner sides (15) of the side walls (14) of said interchangeable container (12) and the outer edges of said work piece platform (8);
(19) the powder sealing element is formed by a silicone plate, the outer dimensions of which are adapted to the inner dimensions of said side walls (14) of said interchangeable container (12);
(20) the work piece platform (8) is connected to said supporting device (20) during the process;
(21) the interchangeable container (12; 112) comprises a recess (33; 133) through which the supporting !device (300; 30) is engaged and in which the supporting device can be displaced;
(22) the recess (33; 133) is sealed against said building space (3) such that no unsolidified material can escape;
(23) the recess (133) is formed in a slot-shaped manner in the direction of displacement of the supporting device and is sealed by means of a tape (200) mounted to the wall of said interchangeable container above said recess and being pressed against the container wall surrounding said recess (133) by said work piece platform (108);
(24) the tape (200), at its other end, is clamped in the region of the lower edge of said interchangeable container and has a constant length between the points at which it is clamped;
(25) the tape is tensioned at the lower side of said work piece platform via at least two slideways (202, 203) arranged in the vicinity of the edges of said work piece platform;
(26) the tape is formed as a steel tape;
(27) the supporting device (40) engages said interchangeable container (12; 112) from underneath and is connected with a telescoping linear guide for raising and lowering said work piece platform;
(28) a working plate (118) is provided in said building space (3), said working plate comprising a device (121) for clamping said interchangeable container (112) at the bottom side of said working plate (118);
(29) a coupling device (300) for coupling and decoupling said supporting device to said work piece platform (108) is provided;
(30) a controllable heating device is provided in said interchangeable container (12), particularly in its side walls (14) and/or said work piece platform (8);
(31) the supporting device is designed such that a space required for lowering said interchangeable container is provided without displacing said supporting device in the vertical direction; and
(32) the lifting and locking of said interchangeable container is carried out in a single movement and/or with a single mechanism.
According to a core aspect of the invention, an interchangeable container forming a delimiting frame is inserted into said sinter building space, said work piece platform being integrated in said interchangeable container as a bottom and a supporting device being arranged in said interchangeable container, on which said work piece platform is resting during operation of the laser sintering machine.
Thus, the novel interchangeable container insertable into said sinter building space is substantially composed of two core components, one being a shaft-like outer portion forming the delimiting frame and the other one being the regular work piece platform which is integrated in this shaft-like portion in a height-adjustable fashion.
When building the part in a layer-by-layer fashion, i.e. layer thickness by layer thickness, the container bottom within the delimiting frame is lowered gradually, and the area above the work piece platform is repeatedly filled with powdery sinter material, which is carried out in-a conventional manner by the coating device.
Advantageously, however, there is no need to also build a peripheral rim. It is fully sufficient to sinter only the actual work piece located within the sturdy interchangeable container and the sinter material, not being sintered, deposited therein and protected against deformation.
As soon as the last layer of the part is sintered, the work piece platform can be lowered via the supporting device into a lower portion and by means of locking elements such as sliding plugs which can be inserted into bores aligned with each other between the walls of the interchangeable container and the work piece platform, the container bottom is firmly connected with the container side walls. This connection may then be released from the supporting device and lifted off and withdrawn from the building space. This can be done trouble-free in the hot state. The cooling of the container, the part contained in it and the sinter material takes place outside the sintering machine.
Immediately after withdrawing the interchangeable container, a new interchangeable container can be inserted, its bottom connected with the supporting device and thereafter unlocked from the side walls of the interchangeable container. After a change-over time of about 15-20 minutes, the sintering machine is again ready for the next laser sintering job.
Therefore, the invention has several advantageous effects on the operation of such a sintering machine. On the one hand, building errors in the periphery do not result in the actual part ending up as a reject. On the other hand, the cooling times of the part and the material surrounding it are transfered out of the sintering machine.
The sintering machine is very rapidly made available again for a new job. Also, both sinter material and energy are saved.
Advantageously, the interchangeable container, as viewed from the top, has a substantially square or rectangular cross section and comprises four side walls substantially perpendicular to each other. Within these side walls, the work piece platform is guided in a height-adjustable manner.
Basically, it is possible to have the supporting device engage from underneath into the shaft of the container side walls or as well integrate it as an integral part into the interchangeable container. In order to provide stability when using a supporting device firmly mounted in the machine, the rear container wall of the interchangeable container preferably comprises engagement recesses extending in the displacement direction, i.e from the bottom to the top, through which a supporting device adjustable in height in the rear side wall portion of the building space can engage with support arms substantially extending in the horizontal direction. There are means provided for covering the engagement recesses in the area above the work piece platform in a powder proof manner.
The solution where the supporting device for supporting the work piece platform engages the interior of the interchangeable container by means of support arms through one of the side walls of the interchangeable container, is advantageous compared to a solution where one support arm engages the interchangeable container for supporting the work piece platform from underneath, since space which would have to be reserved for the supporting device below the interchangeable container can be saved and used as building space for building larger parts. The solution where the support arms or one support arm laterally engage the wall of the interchangeable container, however, always requires the sealing of the engagement recess for a support arm above the work piece platform in order to prevent powder from falling out.
Advantageously, in a first embodiment of the invention, this is achieved by a device for sealing in the form of a roller shutter secured to the upper edge of the interchangeable container and coming to rest on the inner side of the container wall and covering the engagement recesses when the work piece platform is lowered.
In order to guarantee sufficient sinter powder tightness, holding magnet elements cooperating with the steel roller shutter are arranged. Due to the holding magnet elements, the steel roller shutter closely fits the inside of the rear container wall such that no or only very little powder can fall into the lower machine portion.
In a second embodiment of the invention, the interchangeable container comprises a slot-shaped center recess on the rear wall extending in the longitudinal direction, with a support arm for supporting the work piece platform engaging into said recess. To seal this engagement recess in the area above the work piece platform, a tape, preferably made from steel, instead of the steel roller shutter is provided which is clamped at the upper edge of the rear wall and at the bottom of the interchangeable container, respectively, in a region substantially diagonally opposed to the upper edge. The steel tape is guided along the engagement recess and at the bottom side of the work piece platform and is tensioned via gliding cylinders. The steel tape has a fixed length between its clamping points and due to the guiding along the bottom side of the work piece platform, it is always pressed with the correct length against the engagement recess above the work piece platform. Compared to the embodiment using the steel roller shutter, the embodiment using the tape has the advantage that the tape is less expensive and can easily be replaced when worn or damaged. The tape is nearly free of forces. The previously described roller shutter, however, has a strong spring for winding. Nevertheless, with the tape, there is no need to lock the work piece platform in the lower position. The friction of the seal is sufficient to stabilize the work piece platform.
In the upper portion of the container, holding or hooking elements are provided to limit the replacement process to only a few manual steps. It is of particular advantage if the interchangeable container can be inserted in a drawer-like fashion into the process space, with guides being provided in the region of the side walls of the process space and the interchangeable container being equipped at its upper end with supporting angles and the like laterally extending away and resting on the guides of the process space.
In an alternative embodiment, the laterally protruding supporting angles provided at the interchangeable container are not resting on guides in the region of the lateral walls of the process space, but are fastened from underneath, lifted and pressed against the working plate by a clamping device which is provided at the working plate provided in the process space and extending horizontally and having a recess corresponding to the contour of the interchangeable container.
Preferably, the support arm comprises a coupling device permitting very easy coupling to and decoupling from the work piece platform.
Preferably, a hoist is further provided, which can be driven into or next to the building space and on which the interchangeable container can be transported.
In the prior art laser sintering machines, the entire building space is heated. This type of building space heating is relatively slow and energy intensive. Using a heating device which is integrated into the interchangeable container, the bottom thereof or its walls, the heating can be suitably adapted to the thermal requirements of the laser sintering process.